In 1999 the USPS included from their Celebrate the Century Series stamps for the 1950s. This stamp #3187a, for 33c, was issued on May 26, 1999.
This is a First Day Cover available for purchase at Mystic Stamp for the Polio Vaccine Developed Stamp.
#3187a – 1999 33c Celebrate the Century - 1950s: Polio Vaccine Developed
“… In 1947, U.S. physician Jonas Salk began research on the polio virus at the University of Pittsburgh School of Medicine… In 1954, tests were done on an even larger scale. The vaccine, injected with a needle, was found to reduce the incidence of polio. The vaccine was released for use in the U.S. on April 12, 1955.Dr. Albert Sabin also contributed to the victory over polio. He discovered that live, weakened virus, administered orally, would provide immunity over a longer period of time than killed, injected virus. After extensive research and testing, the oral polio vaccine was approved for use in the U.S. in 1961.”